Exchange SMTP load balancing

Question

Exchange SMTP load balancing

Mikhail Firsov 1,881

Hello,
Does anyabody know whether some kind of smtp load balancing solution exists for Exchange, like ARR for http?

Thank you in advance,
Michael

Accepted answer

1 additional answer

Your answer

Answer 1

Andy David - MVP 157.8K MVP Volunteer Moderator

I haven't seen anything that I would call a reverse proxy for SMTP simply because its probably not something that is really required.

Most orgs either drive SMTP traffic through a load balancer like a F5 which routes to an "Edge" type SMTP gateway or simply have multiple "Edge" type SMTP Gateway servers that directly accept and route internet inbound and outbound messages and are all part of the mx record.

I think the biggest question I would have about a reverse proxy" for SMTP is how it would handle anti-malware and anti-spam checks. Not sure if something like even exists honestly.

I have never tried this and do not know offhand anyone who has:
https://docs.nginx.com/nginx/admin-guide/mail-proxy/mail-proxy/
But I think in most cases, the thought for these are for client use rather than as a reverse proxy between mail servers themselves.

Mikhail Firsov 1,881 Reputation points

2020-11-09T12:58:24.48+00:00

"... because its probably not something that is really required" - why not? ARR serves as free HTTP load balancer for small companies (maybe not only for small) and I find ARR strange to be the HTTP load balancer while not offering smtp load balancing. If a company have only 2 or 3 Exchange servers why not have the ability to load balance both smtp and http? Paying thousands of dollars for just 2-3 servers ...? seems a bit excessive in this case.
Andy David - MVP 157.8K Reputation points MVP Volunteer Moderator

2020-11-09T13:03:38.647+00:00
My personal thoughts:

SMTP is traditionally not something a client "interacts" with directly, other than a SMTP / POP client sending mail through it ( and port 587 has really become the standard for client submittal)

SMTP can already balance itself for free with the same mx record pointing to multiple SMTP MTAs.

A lot of SMTP gateways are already sitting in a DMZ like architecture and simply pass the messages to the internal mail servers.
Mikhail Firsov 1,881 Reputation points

2020-11-09T13:56:11.7+00:00

Agree, but I thought that extending ARR functionality to smtp protocol would allow to publish a single mx record (mail.contoso.com = ARR server) and that server would just relay the incoming mail to any internal mail server (if it's up and running) - this configuration would require only one mx record and one external ip...
Andy David - MVP 157.8K Reputation points MVP Volunteer Moderator

2020-11-09T14:02:45+00:00

In that case it wouldn't be really a reverse proxy as much as a simply relay which you could do with an a generic IIS server with SMTP enabled.

I'm not disagreeing that functionality would be nice to have, I'm just thinking its probably something that not a lot of people have asked for and therefore doesn't exist- at least not as a reverse proxy feature.
Mikhail Firsov 1,881 Reputation points

2020-11-09T14:32:32.303+00:00

AndyDavid, thank you very much for your help!

Regards,
Michael
Lydia Zhou - MSFT 2,386 Reputation points Microsoft Employee

2020-11-10T02:05:05.23+00:00

It's great that you can get useful information from above replies. If you have other issues about Exchange, please feel free to post here.

If the response is helpful, please click "Accept Answer" and upvote it.
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

Answer 2

Deleted

This answer has been deleted due to a violation of our Code of Conduct. The answer was manually reported or identified through automated detection before action was taken. Please refer to our Code of Conduct for more information.

4 deleted comments

Comments have been turned off. Learn more

Share via

Exchange SMTP load balancing

1 additional answer

Your answer